Multipurpose food mixing appliance specially adapted for kneading dough

Abstract

A multipurpose electric food mixing appliance specially adapted to mix and knead bread dough in combination with a blender device utilizes one power source to drive both the blender and the mixer. The appliance can sense when dough is properly kneaded and automatically shut itself off. The load on the appliance motor during kneading of the dough is monitored by monitoring the power supplied to such motor and the motor is stopped when the load on the motor begins to decrease after a period of increasing load. With an A.C. motor, the phase angle of power supplied to the motor while keeping the speed of the motor substantially constant is a measure of the load on the motor.

We claim: 
     
       1. A food mixing appliance adapted to knead dough comprising: an A.C. electric motor;   a mixing receptacle;   kneading implement means for kneading dough within the mixing receptacle;   drive means coupling the electric motor to the kneading implement means;   motor control means for controlling the phase angle of A.C. power applied to the motor to maintain speed of rotation of the motor substantially constant during kneading of dough;   sensing means for monitoring the power required to maintain the speed of rotation of the motor constant during kneading of dough, said sensing means monitoring the phase angles of A.C. power applied to the motor, increasing phase angles indicating increasing power being applied to the motor and decreasing phase angles indicating decreasing power being applied to the motor; and   means for stopping operation of the motor when the sensing means for monitoring the power required to maintain the speed of rotation of the motor constant detects that the power required to maintain the speed of rotation of the motor constant begins to decrease after a period of increasing required power.   
     
     
       2. A food mixing appliance according to claim 1, wherein the sensing means for monitoring the power required to maintain the speed of rotation of the motor constant averages the phase angles monitored over set periods of time. 
     
     
       3. A food mixing appliance according to claim 2, wherein the set periods of time are each a period of time representing 256 cycles of the A.C. power. 
     
     
       4. A food mixing appliance according to claim 2, wherein the means for stopping operation of the motor stops operation of the motor only if the power required to maintain the speed of rotation of the motor constant decreases over a preset number of consecutive periods of time. 
     
     
       5. A food mixing appliance according to claim 4, wherein the preset number of consecutive periods of time is two consecutive periods of time. 
     
     
       6. A food mixing appliance according to claim 1, wherein the motor control means includes tachometer means to monitor the speed of rotation of the motor. 
     
     
       7. A food mixing appliance according to claim 6, wherein the motor includes a fan which rotates with the motor and has a plurality of fan blades, and wherein the tachometer means includes a sensor positioned adjacent the fan so as to produce an electrical signal each time a blade of the fan passes the sensor during operation of the motor. 
     
     
       8. A food mixing appliance according to claim 1, wherein the means for stopping operation of the motor will stop operation of the motor if the power supplied to the motor over a preset period of time indicates that the motor is overloaded. 
     
     
       9. A food mixing appliance according to claim 8, wherein the means for stopping operation of the motor will start operation of the motor a preset rest period of time after operation has been stopped because of an indicated motor overload. 
     
     
       10. A food mixing appliance adapted to knead dough comprising: an electric motor;   fan means coupled to the electric motor, said fan means having a plurality of fan blades, the speed of rotation of the fan means being proportional to the speed of rotation of the motor;   a mixing receptacle;   kneading implement means for kneading dough within the mixing receptacle;   drive means coupling the electric motor to the kneading implement means;   motor control means for controlling the phase angle of A.C. power applied to the motor to maintain speed of rotation of the motor substantially constant during kneading of dough;   tachometer means for monitoring the speed of rotation of the motor, said tachometer means including a sensor positioned adjacent the fan means so as to produce an electrical signal each time a blade of the fan means passes the sensor during operation of the motor;   sensing means for monitoring the power required to maintain the speed of rotation of the motor constant during kneading of dough, said sensing means monitoring the phase angles of A.C. power applied to the motor, increasing phase angles indicating increasing power being applied to the motor and decreasing phase angles indicating decreasing power being applied to the motor; and   means for stopping operation of the motor when the sensing means for monitoring the power required to maintain the speed of rotation of the motor constant detects that the power required to maintain the speed of rotation of the motor constant begins to decrease after a period of increasing required power.   
     
     
       11. A food mixing appliance adapted to knead dough comprising: an electric motor;   a base for mounting the electric motor, said electric motor being oriented and attached perpendicularly to said base, said motor having a housing with a horizontally oriented platform member disposed above said motor, an output armature shaft extending through said motor and said platform member and having an output armature shaft lower end portion extending below the motor and an output armature shaft upper portion extending above the motor and through the platform member, and a fan having multiple, evenly spaced fan blades attached to said upper portion of said output armature shaft and disposed above and adjacent to said platform member;   a mixing receptacle having a central pillar;   kneading implement means for kneading dough within the mixing receptacle;   drive means coupling the electric motor to the kneading implement means, said drive means including a drive train operably attached to the lower end portion of said output armature shaft, said drive train ending with a drive socket, and a drive shaft adapted to fit inside said central pillar, said drive shaft having an upper end portion being capable of driving a mixing element disposed within said receptacle, and a lower end portion operably adapted to operably attach to said drive socket;   a sensing element disposed on the platform member adjacent to said fan for sending an output signal as each blade of said fan passes by said sensing element;   control means including means responsive to the output signal sent by said sensing element for adjusting the power supplied to said motor to maintain the speed of said motor within a selected operating range;   sensing means for sensing the load on the motor as it drives the kneading implement means during kneading of dough; and   means for stopping operation of the motor when the sensing means senses that the load on the motor begins to decrease after a period of increasing load.   
     
     
       12. A home food mixing appliance adapted to knead small batches of dough for domestic bread making comprising: an electric motor which includes a fan which rotates with the motor and has a plurality of fan blades;   a mixing receptacle of size to hold an amount of dough no larger than normally considered adequate for domestic bread making;   kneading implement means for kneading dough within the mixing receptacle;   drive means coupling the electric motor to the kneading implement means;   a sensor positioned adjacent the fan so as to produce an electrical signal each time a blade of the fan passes the sensor during operation of the motor to provide a means to monitor the speed of the motor;   motor control means cooperable with the means to monitor the speed of the motor;   means for monitoring the power required to maintain the speed of rotation of the motor constant as it drives the kneading implement means during kneading of dough; and   means for stopping operation of the motor when the means for monitoring the power required to maintain the speed of rotation of the motor constant detects that the power required to maintain the speed of rotation of the motor constant begins to decrease after a period of increasing required power.   
     
     
       13. A food mixing appliance according to claim 12, wherein: the motor is an A.C. motor;   the motor control means controls the phase angle of A.C. power applied to the motor; and   the means for monitoring the power required to maintain the speed of rotation of the motor constant monitors the phase angles of the A.C. power applied to the motor, increasing phase angles indicating increasing power being applied to the motor and decreasing phase angles indicating decreasing power being applied to the motor.   
     
     
       14. A food mixing appliance according to claim 13, wherein the means for monitoring the power required to maintain the speed of rotation of the motor constant averages the phase angles monitored over a set period of time.